Vertebrate evolution

General considerations

Organic evolution on Earth began in the border zone between the Earth's crust and its atmosphere. The interaction of solar energy with the Earth's surface, largely covered by the oceanic basins, resulted in mainly salt solutions. These would become an essential component of life and, eventually, of nervous systems. If we accept the view that the oceans and their rocky surroundings became the fertile grounds for organic evolution, then rock formations and marine sediments become important witnesses for evolution. The remains of early life in rocks and sediments had been known for a long time but it was only in the second half of the nineteenth century that their significance was recognised by science as documentary evidence of the evolution of life on Earth. Up to that time it was the teaching of the Church that the Earth and its inhabitants were created by a single act of God about 4000 years ago. This view was also accepted by scientists, although later modified by the French anatomist Cuvier (1769–1832) who assumed several creative acts in order to explain the different fossil findings in different geological periods. By the fifteenth century the study of mineralogy had attracted Bauer, a German doctor, who studied closely excavations made for the mining industry and who laid the foundation for a close relation between evolution and geology. Berry (1968) has given an excellent account of the interrelation between the exploration of the Earth's crust and the understanding of evolution.